Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with transitional graphical user interface showing a first image of the claimed design; and,

FIG. 2 is a front view showing a second image thereof.

The transitional graphical user interface transitions sequentially between FIG. 1 and FIG. 2. The process or period in which an image transitions to another image forms no part of the claimed design.

The gradient background of the graphical user interface is claimed subject matter.

The longer-length broken-line showing of a display screen and the intermediate-length broken-line showing of a display screen boundary are included for the purpose of illustrating unclaimed environmental structure. The remaining broken lines represent portions of the graphical user interface that form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 